Capillary Number - Christopher Sparages: Difference between revisions

Squeezing, dripping, and jetting are other events that occur in droplet microfluidics. In the case of squeezing mode, low capillary numbers are used to produce droplets, in doing so a pressure gradient is formed across the droplet upon being formed. They droplets travel as plugs. In the case of dripping mode, viscous shear stress and interfacial tension compete as the capillary number increases with flow rate and the droplet fluid is broken up along its pathway through the channel. The droplets travel as small drips. Lastly, by increasing the capillary number and forces farther jetting occurs, resulting in droplets traveling as either spheres or plugs ([[Droplet_Microfluidics:_T-Junction_-_Lina_Wu | Droplet Microfluidics: T-Junction]]).¹⁴

Capillary valves have been implemented frequently on CD fluidic platforms. The idea behind them is that they are controlled by surface tension, which occurs when the cross-section of the hydrophilic capillaries drastically expands. This expansion typically leads into a reservoir for the liquid to gather in. The pressure resulting from the rotation of the CD device increases the forces and capillary number in the channel. As a result, the capillary valve can be overcome and droplets can form and progress into the larger expanded portion of the microfluidic channel. Based on the forces and capillary number affecting the fluid, determines the potential of overcoming the forces of the capillary valve.¹³